1. Field of the Invention
The present invention relates to an image pickup apparatus, and more particularly, to a structure for cooling an image pickup element.
2. Description of the Related Art
Image pickup elements convert light into electric signals. When the temperature of an image pickup element increases, unnecessary noise components are superimposed on signals output by the image pickup element, which leads to reduction in image quality. Therefore, it is essential to cool the image pickup element in an apparatus including the image pickup element.
Japanese Patent Laid-Open No. 2005-354637 discloses a structure in which an image pickup element is mechanically connected to an apparatus housing with a heat dissipating member so that heat generated by the image pickup element is dissipated to the outside through the surface of the apparatus by heat conduction. This method is inexpensive and can be achieved by a simple structure, and is therefore widely used in product assemblies.
Japanese Patent Laid-Open No. 2009-33718 (US Patent Application Publication No. 2009/0002549) discloses a structure in which an image pickup element is forcedly air-cooled by forming an air flow channel around the image pickup element. With this method, the cooling effect can be increased and the temperature of the apparatus housing can be prevented from increasing. Thus, this method is more advantageous than the above-described method using heat conduction in many aspects.
Image pickup apparatuses, such as digital cameras, generally include a zooming mechanism which changes an angle of view of an image to be captured by moving one of or more of lens groups included in an imaging optical system. In addition, recently, structures in which an image pickup element, on which an object image is formed, is moved together with movable lens groups in a zooming operation have been proposed as a way to reduce the size of the imaging optical system and increase the reliability.
In the structures in which the image pickup element is moved in the zooming operation, the above-described cooling methods have the following problems.
That is, with regard to the cooling method using heat conduction, it is difficult to apply the cooling method to the structure in which the image pickup element is moved since the image pickup element is required to be mechanically connected to the apparatus housing or the like with the heat dissipating member.
With regard to the forced air cooling method, there are difficulties in forming a direct air flow channel around the image pickup element. More specifically, since the position of the image pickup element changes during the zooming operation, it is necessary to move the air flow channel in accordance with the position of the image pickup element. This makes the cooling effect unstable. Accordingly, it becomes necessary to increase the size of the apparatus to form an effective air flow channel depending on the arrangement of the image pickup element and the space around the image pickup element. In addition, since the image pickup element functions as a part of a lens mechanism, the air flows in the lens. As a result, dust enters the lens and scatters in the lens.